1. Field of the Invention
The present invention relates to a composition used for a resist pattern that is formed in manufacturing a semiconductor device. The present invention also relates to a method for forming a resist pattern which includes forming a fine space pattern of resist, exceeding exposure limits (resolution limits) of light sources of available exposure devices by thickening the resist pattern; a semiconductor device, and a method for manufacturing the semiconductor device.
2. Description of the Related Art
Semiconductor integrated circuits are becoming more highly integrated, and LSIs and VLSIs are being put into practical use. Accompanying this trend, the interconnection patterns extend to regions of 0.2 μm or less, and the smallest patterns extend to regions of 0.1 μm or less. A lithographic technique is extremely important in forming fine interconnection patterns. In the lithographic technique, a substrate is coated with a resist film, is selectively exposed, and thereafter, is developed to thereby form a resist pattern. The substrate is subjected to a dry etching treatment by using the resist pattern as a mask, and thereafter, by removing the resist pattern, the desired pattern, for example, an interconnection pattern is obtained. In forming a fine interconnection pattern utilizing the lithographic technique, it is necessary to make the light source of the exposure device be a short wavelength, as well as to develop resist materials which have high resolution and are suitable to the characteristics of the light source.
However, in order to make a light source of an exposure device be a short wavelength, it is necessary to improve the exposure device, which results in very high costs. Further, the development of new resist materials suitable for an exposure with light of short wavelength is not easy.
To overcome the above technical problems, there has been proposed a technique that a resist pattern formed from a conventional resist material is thickened with a resist pattern thickening material (hereinafter, sometimes referring to as “resist swelling material”) capable of forming a fine space pattern of resist. For instance, Japanese Patent Application Laid-Open (JP-A) No. 10-73927 discloses a technique called RELACS. According to the disclosure, a resist pattern is formed by exposing a resist film with an exposure light such as KrF (krypton fluoride) excimer laser light having a wavelength of 248 nm, which is a deep ultraviolet light. Thereafter, a water-soluble resin composition is applied over a surface of the resist film to form a coated film so as to cover the resist pattern. The coated film and the resist pattern are subjected to a cross-linking reaction at the interface thereof by the effect of residual acid included in the resist pattern, so as to thicken the resist pattern (hereinafter, the thickening of the resist pattern sometimes referring to as “swelling”). In this way, the spaces between the individual resist patterns are shortened, and a fine space pattern of resist is formed. Thereafter, a desired pattern (e.g. interconnection pattern) having the same dimension as the space pattern is formed.
In the RELACS technique, however, there are the following problems. The KrF resist for use is formed of an aromatic resin composition including a novolak resin, naphthoquinonediazide resin or the like. An aromatic ring contained in the aromatic resin composition allows KrF excimer laser light (wavelength: 248 nm) to pass through, but absorbs ArF excimer laser light (wavelength: 193 nm) having a shorter wavelength than the KrF excimer laser light and does not allow the ArF excimer laser light to pass through. Therefore, when the KrF resist is used, ArF excimer laser light cannot be used as the exposure light, which makes it impossible to from a fine interconnection pattern, etc. Moreover, there is a problem in the RELACS technique that the resist swelling material is effective in thickening or swelling the KrF resist, however, ineffective in thickening or swelling the ArF resist.
From the standpoint of forming a fine interconnection pattern, it is desirable to use a light of a shorter wavelength than KrF excimer laser light, e.g., ArF excimer laser light, as the light source of the exposure device. When an x-ray or electron beam having a shorter wavelength than the ArF excimer laser light is applied as exposure light to form the pattern, however, it results in high cost and low productivity. Thus, the utilization of ArF excimer laser light is desired.
As mentioned above, in the RELACS technique, the aforementioned resist swelling material does not efficiently work on ArF resist pattern. The present inventors have proposed a resist pattern thickening material capable of forming a fine pattern by improving affinity with the ArF resist pattern caused by a surfactant (see JP-A No. 2003-131400). However, the composition of this resist pattern thickening material sometimes causes dependency on the pattern size before thickening, that is, when the pattern size before thickening increases, the reduced amount of the pattern size after thickening may increase in proportion to the increase. Moreover, when a resist pattern is formed from a conventional resist composition, the resist pattern along the narrow side directions, or a region where elements of the resist pattern are sparsely located to each other, i.e. a region where space between the elements of the resist pattern is wide, has a small thickened amount, whereas the resist pattern along the wide side directions, or a region where the elements of the resist pattern are closely located to each other, i.e. a region where a space between the elements of the resist pattern is narrow, has a large thickened amount. Accordingly, a thickening amount of the resist pattern largely varies depending on the direction and/or spacing variations of the resist pattern. Thus, there was a problem that when the resist pattern thickening material was used for a space pattern, on an interconnection layer of LOGIC LSI where various sizes of resist patterns are used, the burden on designing an exposure mask could not fully be alleviated.
Thus, the current situation is that there has not yet been developed a technique which can use ArF excimer laser light as the light source of an exposure device during patterning, which can sufficiently thicken ArF resist pattern or the like that cannot be thickened by using the aforementioned resist swelling material used in the RELACS technique, and which can easily form a fine space pattern of resist or an interconnection pattern at low cost. Therefore, it is desired that such technique be developed.
The present invention aims at solving the shortcomings in the prior art, and can achieve the following objects.
An object of the present invention is to provide a resist composition, which can utilize ArF excimer laser light, for example, as an exposure light during patterning; which is suitably utilized when a resist pattern thickening material is applied over a surface of a resist pattern which has been formed by exposure of light and a developing treatment so as to uniformly thicken a resist pattern, e.g., in form of space pattern, with the resist pattern thickening material regardless of the direction, spacing variations and the like of the formed resist pattern and without depending on the components of the resist pattern thickening material; which is capable of forming a fine space pattern of resist, exceeding exposure or resolution limits of light sources of available exposure devices at low cost, easily and efficiently.
Another object of the present invention is to provide a method for forming a resist pattern which, during patterning a resist pattern, can utilize ArF excimer laser light as an exposure light; which can thicken a resist pattern, e.g. in form of space pattern, regardless of the direction, spacing variations and the like of the resist pattern and without depending on the components of the resist pattern thickening material; and which is capable of forming a fine space pattern of resist, exceeding exposure or resolution limits of light sources of available exposure devices at low cost, easily and efficiently.
Yet another object of the present invention is to provide a method for manufacturing a semiconductor device in which, during patterning a resist pattern, ArF excimer laser light can be utilized as a light source; a fine space pattern of resist, exceeding exposure or resolution limits of light sources of available exposure devices, can be formed, regardless of the direction, spacing variations and the like of the resist pattern and without depending on the components of the resist pattern thickening material; and high-performance semiconductor devices having fine interconnection patterns formed by using the space pattern of resist can be efficiently mass produced, and is to provide a high-performance semiconductor which is manufactured by the method for manufacturing a semiconductor device and has fine interconnection patterns.
In view of the above-mentioned shortcomings, the inventors of the present invention have investigated vigorously, and have obtained the following findings. Specifically, when a resist pattern formed from a conventional resist composition is thickened by using a resist pattern thickening material, the resist pattern along the narrow side directions, or a region where elements of the resist pattern are sparsely located to each other, i.e. a region where space between the elements of the resist pattern is wide, has a small thickened amount due to a small amount of fogging exposure near the pattern, whereas the resist pattern along the wide side directions, or a region where the elements of the resist pattern are closely located to each other, i.e. a region where a space between the elements of the resist pattern is narrow, has a large thickened amount due to a large amount of fogging exposure. Accordingly, a thickening amount of the resist pattern largely varies depending on the direction and/or spacing variations of the resist pattern. However, when an alicyclic compound having a melting point of 90° C. to 150° C. is contained to the resist composition, the resist composition interacts with the resist pattern thickening material regardless of the amount of the exposure dose, and thus the resist pattern is efficiently and uniformly thickened, regardless of the direction and/or spacing variations of the resist pattern, components of the resist pattern thickening material, and the like.